Ants of New York

Photograph by Eric Feferberg/AFP/Getty

The insect collection at the American Museum of Natural History holds approximately sixteen million specimens, collected from some of the most remote corners of the world. But until earlier this year, the museum lacked a single ant from a place that scientists have traditionally neglected to look: the sidewalks and street medians of Manhattan. Almost by definition, natural science tends to begin its examination of wildlife only after travelling as far away from people as possible. “There’s this idea that when people come into an area, they make changes, and if you leave things alone then ecology actually happens,” Amy Savage, an ecologist at North Carolina State University, said recently. “But that puts people outside of the ecological process, which isn’t quite right.”

Last summer, Savage collected what would become the museum’s first sample of Manhattan street ants. Along with a parallel sample at North Carolina State, they are quite possibly the only New York street ants in a museum collection anywhere in the world. It’s a small step; there is still no established, comprehensive account of the ant species that live in many cities, including New York. The first definitive survey of ant species across Manhattan’s habitat, which Savage wrote, is currently under review for publication.

Savage, who is thirty-six, grew up in Montana, where she was “always one of those kids who was sitting in the outfield looking at the insects instead of watching the ball,” she said. She began her career as a tropical ecologist, conducting doctoral research in Samoa. “I thought if I could get to a removed-enough place, I would see what really happens, what real ecology is. And I went to the middle of the South Pacific, and still people were a key part of the ant story.” Savage found that, even away from the local villages, ants were more common in areas where people collected or stored fruits and plants. The largest population of the ant she had arrived to study, she realized later, was in a factory that made juice from the plant it liked to eat. “The truth is that we’re another species, and there’s no reason to separate us out and think of us as something that’s not ecology. When I realized that, I got to thinking about what that means for what’s right around us.”

After completing her dissertation, Savage joined a lab at North Carolina State that had an urban-ecology group already in place. For the past three years, usually during the summers, she has been lugging step ladders, temperature loggers, and aspirators—metal-and-plastic assemblies of tubes, piping, and a jar, to suck up individual ants off the dirt—across the city’s parks, sidewalks, and intersections, and up into street trees. The lab has been sending researchers for nearly a decade. They have discovered a handful of ants and other insects that were not known to live in New York, and have found that different species live on streets and sidewalks versus in the parks nearby.

On a recent Monday, Savage and a biologist named Clint Penick found themselves knee-deep in the bushes of Broadway, where they had climbed into a median just south of Lincoln Center. Penick, who is thirty-one, wrote his first scientific paper using research from his Florida back yard; in eighth grade, he played guitar in a band called the Army Ants. (“It was my middle-school mind’s version of what a punk band should be called,” he said.) He can identify some ants by smell. One species in the southern U.S. has an alarm pheromone that smells like chocolate, he said, though “you have to crush their heads to smell it,” and one New York ant smells like citronella. Another, which he helped a non-scientist friend to identify at her Brooklyn apartment, is known as the “odorous house ant,” and smells like blue cheese.

A security guard stopped by to ask Penick if he had a permit. The guard called his manager—“It’s the same thing they were doing last year. Yeah, I remember them”—then left Savage and Penick to turn their attention groundward. The pair sifted clumps of dirt from beside tree trunks, beneath rocks, and under the occasional cinderblock, and found two flat, ant-heavy spots to set up feeding trials. Previous visits had determined that street ants thrive on food scraps that people toss away. This round of study offered the ants oils and food scraps alongside more traditional insect prey—crickets, mostly—to see whether median ants prefer complex fats and oils, such as olive oil, to those found in processed foods. (They still prefer crickets, but of the oils they seem to express a very slight preference for the olive oil, which is most similar to the fats in their natural prey.) Savage and Penick laid out their materials where they found most of their ants, near the pedestrian crosswalks. “Ants like to live under cracks in the pavement, so they live at the edges of the medians,” Penick said. “Also, the ends are closer to the garbage cans.”

Broadway doesn’t always provide ideal lab conditions. In addition to the occasional run-in with a diligent security guard, Penick and Savage have had to sidestep landscapers and watering trucks, and once wasted a good part of a research day before realizing that a crew of groundskeepers had been trailing them from median to median, lagging a few blocks behind, and tossing out their experiments. “Another time, it was pretty clear that a rat had chewed the olive-oil tube,” Savage said.

Beyond any implications for ant ecology, Savage hopes that her work on Broadway will help to recalibrate a field whose models are still cloaked in their tropical origins. Much of what scientists learn about ecosystems still tends to be applied to the kinds of isolated settings that some researchers describe as “islands” of wildlife within a “sea” of agriculture, where the human impact on plant and animal life seems more indirect. “Understanding cities is going to help ecologists move forward and understand big ecological questions in a better, more thorough way,” Savage said. “You have to add people back in.”